In orthogonal frequency division multiplexing (OFDM), if a certain symbol is delayed, that symbol becomes an interference wave against the subsequent symbol, resulting in a decline of a signal to interference and noise ratio (SINR) of the subsequent symbol. In order to prevent this, a guard interval (GI) is provided at the head of the symbol.
In Patent Document 1, there is described a technology of controlling a guard interval length in accordance with a symbol delay amount. The SINR increases as the guard interval becomes longer, but this causes the communication rate to decrease. Accordingly, with this technology, while keeping a balance between the communication rate and the SINR, the guard interval length is so determined that a minimum required SINR can be obtained.
Further, in Patent Document 2, there is disclosed a technology of reducing, in a case where the same sub-carriers are transmitted from a plurality of transmitters, which occurs at a time of, for example, handover, interference between symbols that are transmitted from each of the transmitters. Further, in Patent Document 3, there is disclosed a technology of improving frequency usage efficiency in OFDM.
Patent Document 1: JP 2002-374223 A
Patent Document 2: JP 2005-303826 A
Patent Document 3: JP 2005-252886 A